The present invention relates to a fuel control system for an internal combustion engine for supplying continuously the fuel, which is metered in proportion to the quantity of intake air, to a plurality of fuel injection nozzles under a relatively low pressure.
In order to ensure the optimum engine operation, to minimize the emission of toxic pollutants and to attain fuel economy, the fuel control systems must be such that the fuel may be metered with a higher degree of accuracy depending upon the quantity of intake air and the metered fuel must be distributed among cylinders as uniformly as possible. To these ends, various systems have been devised and demonstrated. For instance, employed in one system are fuel injection nozzles which are fabricated with an extremely higher degree of dimensional accuracy so that their fuel injection characteristics may be as uniform as possible. In another system, fuel metering devices are provided for respective cylinders for individually metering the fuel to be charged into respective cylinders.
The former system has a problem that with the present level of fuel injection nozzle manufacturing techniques it is extremely difficult to fabricate the fuel injection nozzles with uniform fuel injection characteristics. Therefore, of an extremely large number of fuel injection nozzles, those having the similar characteristics must be selected. This is very tedious. In the latter system, the fuel metering devices must be also fabricated so as to have the same characteristics. In addition, the fuel metered by these devices is very small in quantity so that they must be also fabricated with an extremely higher degree of dimmensional accuracy with the inevitable increase in cost.